The institute of electrical and electronics engineers (IEEE) 802.16e standard was adopted in 2007 as a sixth standard for international mobile telecommunication (IMT)-2000 in the name of ‘WMAN-OFDMA TDD’ by the ITU-radio communication sector (ITU-R) which is one of sectors of the international telecommunication union (ITU). An IMT-advanced system has been prepared by the ITU-R as a next generation (i.e., 4th generation) mobile communication standard following the IMT-2000. It was determined by the IEEE 802.16 working group (WG) to conduct the 802.16m project for the purpose of creating an amendment standard of the existing IEEE 802.16e as a standard for the IMT-advanced system. As can be seen in the purpose above, the 802.16m standard has two aspects, that is, continuity from the past (i.e., the amendment of the existing 802.16e standard) and continuity to the future (i.e., the standard for the next generation IMT-advanced system). Therefore, the 802.16m standard needs to satisfy all requirements for the IMT-advanced system while maintaining compatibility with a mobile WiMAX system conforming to the 802.16e standard.
Recently, a wireless communication system including a relay station (RS) has been developed. The relay station serves to expand cell coverage and improve transmission performance. The cell coverage may be expanded as a base station provides service to a mobile station located at the coverage boundary of the base station by using a relay station. Furthermore, since the relay station enhances the reliability of signal transmission between the base station and the mobile station, transmission capacity can be increased. Even when a mobile station is within the coverage of the base station, the relay station may be used in the case where the mobile station is located in a shadow zone.
A frame structure of a system adopting such a relay station may be different from a frame structure of a system without the relay station. A portion of the frame may be used just for communication between a base station and a mobile station or between a relay station and a mobile station, while another portion of the frame is used for communication between the base station and the relay station. A region in which the mobile station can transmit/receive data to/from the base station or the relay station is limited, and thus Hybrid Automatic Repeat request (HARQ) feedback or the like is also limited.
In the system adopting the relay station, there is need for a new frame structure for efficiently performing HARQ feedback.